This invention relates to thermostatic expansion valves and, more particularly, to a vibration damping device for preventing the internal valve components from resonating during operation.
Thermostatic expansion valves are used in air conditioning and refrigeration systems to control refrigerant flow to the evaporator under varying heat load conditions. A typical construction of this type of valve is illustrated in U.S. Pat. No. 3,537,645 and such construction usually employs a ball and pad assembly, push-pin, and rider pin suspended between a diaphragm and a spring. The spring/mass system is inherently underdamped and thus susceptible to resonance initiated by pressure pulses from the compressor. The resultant resonance could cause the valve to open and close, amplifying pressure pulsation upstream of the thermostatic expansion valve. Under certain conditions, the system piping could be forced into resonance, producing an unwanted audible noise.
One prior attempt at controlling system noise was to install mufflers in the system. These were typically placed in the suction or discharge piping at the compressor. This, however, did not always solve noise problems in systems and also added considerable expense to the system. Another prior method of solving the problem was to change the configuration of the high pressure piping between the receiver and the valve. This caused a shift in the resonant frequency of the piping, making it more difficult for the valve oscillation to force the piping into resonance. This was a trial and error procedure and did not always prove to be effective.
It is therefore an object of this invention to provide an inexpensive and effective device for damping vibrations in a thermostatic expansion valve.